@Hun boy Apologies for the delayed response here.
If I understand your question correctly you wish to have users mount to a particular directory of your Azure file share. You cannot have them mount the specific directory, but you can set permissions on the directory and files. See here for information on mounting the file share.
Assigning permissions for the directories will depend on whether you are using Active Directory Domain Services (AD DS) or Azure Active Directory Domain Services (Azure AD DS). To assign permissions with AD DS you will need to review this page. If you are using Azure AD DS please review this storage-files-identity-auth-active-directory-domain-service-enablepage.
Hopefully this helps! If you have further questions do let us know and we will be happy to help.
-----------------
Please don’t forget to "Accept the answer” and “up-vote” wherever the information provided helps you, this can be beneficial to other community members.